Double acting valve



Sept. 17, l1940. H. c. BUFFINGTON 2,215,115

DOUBLE ACTING VALVE Filed June 22, 1938 3 Sheets-Sheet l IMI .0, $7/

HARRY C. BUFFINGTON sept. 17,1940.

H.C. BUFFINGTON DOBLE ACTING VALVE Filed June 22, 1938 3 Sheets-Sheet 2HARRY C. BUFFINGTON Sept. 17, 1940- H.,fc. BUFFINGTON 2,215,115

DOUBLE ACTING VALVE l Filed June 22, 1938 s sheets-sheet s LIFTINGPOSITION HOLDING LowEmNc PosmoN l Patented spr. 17,1940 i UNITED s'rAres 'PATENT OFFICE DOUBLE 'ACTING vALvE 4 Harry C.Bullingtom'sprlngiield, Ill., assigner to BakerManuiacturlngCo.,Springiield, Ill., a

corporation of Illinois Application June zz, 193s, serial No. 215,095

This invention relates to valvesy including sliding or reciprocal coresfor operating unbalanced-poppet valves.

More particularly, the invention relates to a 5 valve mechanismincluding an unbalanced check valve and a reciprocal core for operatingthe check -valve simultaneously with the directing of fluid underpressure `to and from a pair of iluid pressure jacks, to eilect fouroperating conditions for the jacks. In tractor operated bulldozers,trailbuilders, snowplows and the. like, the lwork implement blade isusually. controlled by a pair of iluid presl sure jacksa 'I'he jackcylinders are preferably l llsupported by the push beams carrying theim-` plement blade while the piston rods extending from theF cylindersact against the tractor'body or track 'frames oi the tractor. When thepiston rods are carried by the track frames, and when 'theV pair ofjacks are in iluid intercommunlcation,

movement of the track frames infgoing over uneven ground does not'affectthe level of the work -implement blade since iluid .will flowback and forth between the cylinders.

Valves for controlling 'the flow of ii'uld under pressure to and fromthe cylinders shouldhave four operating positions. In one position oithe valves,l the fluid under pressure should be supplied to the tops ofthe cylinders for raising the 3'0 work implement blade. In the secondoperating position q:the .iluid in the cylinders should be 'sealed tohold' the. work implement .blade in a preset position. In this positionof the valves,

.however, the fluid inthe cylinders should be permitted to flow backand@ forth between the pair of cylinders so as not to aiect the positionof th implement blade due to movement of the track frames in goingoveruneven ground. In

'the third operating position, the valves shouldv4 4o supply fluid under'pressure to the bottoms of `esofiml the work implement blade of abulldoze snow-plow, or the vlike by manual reciprocation oiaslldabl"valve core. t

While thelvalves will beparticularly hereinafter described in connectionwith the control of a hydraulic liquid for operating a pair oihydrauwith parts shown in elevation, taken along the mm. '(cLzr'I-u -licjacks, it should be understood that these valves have wide usage incontrolling flow of ids under pressure. It is, then, an object of thisinvention to provide a valve mechanism for controlling iiow of 5 kfluidunder pressure by a simple reciprocating novement. 1

' Another object of the invention is to provide a valve having aslidable'or reciprocable core together with an unbalanced checkvalveoperated 10 by the core. A

Another object of this invention is to provide a valve mechanism forc'oxi'trolling-ow of a liquid 'under pressure by a slidable core memberhaving balanced end thrusts under all operating condi-l. 15 tions toprevent undesired movements of the core. Other and further objects ofthe invention will Abecome apparent to those skilled in the art from thefollowing detailed description of the annexed sheets of drawings whichdisclose a preferred em- 20 bodiment ofthe invention.

On the drawings: Figure l is a. somewhat diagrammatic view, partly invertical cross section, showing the valve mechanism of this inventionoperatively con- 25 nected for controlling flow o1 a hydraulic liquid toand froma of hydraulic jacks. i

Figure 2 is a vertical cross-sectional view, with parts in elevation,taken longitudinally through the. valve mechanismv ofthis invention.

Figure 3 i's a horizontal cross-sectional view, with parts in elevation,taken along the line III--IlI of Figure 2. Y

Figure 4. is a vertical cross-sectional view,

3 line IV-IV of Figure 3. Figure is a vertical cross-sectional view,with a part shown in elevation, taken along the line V-V ofliigure 2.

Figure 6'is a vertical cross-sectional view, with parts shown inelevation, taken along the line VI-l-VI of Figure 2.

. Figures '1 to 10 inclusive are horizontal crosssectional views, withparts shown in elevation, of

the valve Ymechanism illustrating the four 'oper- 45 ating positions ofthe valve.

' Asshown onthe drawings: In Figure 1 the reference numeral I 0 desig"nates generally avalveaccording to this inventior havingoprating leveril and handle l2 `50 on the end ofthe lever. The valve l0 is providedwithan inlet chamber i3.' a return chamber'll,

and operating chambers I5 and I6.

The inlet chamber I 3 receives the end of a pipe line I1. The pipe lineI1 is connected to the dis- A55 hoses or tubes 23 and 24. The ends oftheA tubes 23 and 24 respectively enter cylinders 25 and 26.

The operating chamber I6 of the valve I0 receives the end of a pipe 21.The other end of the pipe 21 has a T coupling 21a thereon communicatingwith flexible hoses'or "ibes 28 and.l 29. The hoses 28 and 29respectively enter the bottoms of the hydraulic :lack cylinders 26 and26.

The jack cylinders 26 and 26 each have a piston 30 therein and a pistonrod 3l secured to the piston and extending through the bottom heads ofthe cylinders.

'I'he cylinders 25 and 26 are preferably carried by the push beams of abulldozer, snowplow or the like while the piston .rods 3I are preferablycarried by the track frames 'or tractor body portion of the bulldozer orsnowplow.

A manipulation of the lever II of the valve I0 controls flow of fluidfrom the various chambers of the valve to supply oil from the tank 20either to the tops of the cylinders 25 and 26 or to the bottoms of thecylinders 26 and 26. The valve also can lock-.the oil in the cylinders25 and 26 so that the same cannot return through the valve to the oiltank 20. In another operating position the valve permits free ow of oilbetween the cylinders and the oil tank.

As'best shown in Figures 2 and 3, the valve II) comprises a casing 40defining a cylindrical control chamber 4I. The ends of the chamber 4Iare closed by end caps 42 and 43 respectively. The end caps 42 and 43have feet 44 and 45 thereon for bolting the valve to the tractor orother supporting structure. Gaskets such as 46 vcan be the tops ofhydraulic interposed between the end caps 42 and 43 and,

the ends of the casing 40.

The end cap 43 has an annular portion 43a v extending outwardlytherefrom to define a chamber for packing 41. The packing 41 is held inthe chamber by a packing ring 48. The packing ring and end cap 43 havealigned openings 49 therethrough for receiving in slidable relationthereto an operating rod 58. The rod 50 is pivoted to the operatinglever II as at 5I; The end.

of the lever II is pivotally connected to the end cap 43 through a link52. ItiStIius evident that a swinging of the lever II toward and awayfrom thefcasing 40 will move the rod 50 into and. out of the casing.

The inner end of the rod 50 is secured to`a cylindrical core 53 slidablymounted in the control chamber 4 I The casing 40 has an integral housingstructure 40a on the top thereof, a second integral housing structure40h on the bottom thereof and a third integral housing structure 40c onthe side thereof. i

4I'he housing structure 40a defines the inlet chamber I3 and the returnchamber I4. The housing structure 49h defines the :operating chamber I6.The housing structure 40c defines the operating chamber I5.

The inlet Vchamber I3 communicates through a passageway 55 with thereturn chamber I4 as best shown in Figure 2. `Ayalve seat 56 isprovidedin this passageway 55 and receives a slidable relief valve 51 thereon.The relief valve 51 is slidably mounted in a cylindrical compartment 58of the housing structure 40a. A boss plug 59 is threaded into thecylindrical compartment 58. A tension adjusting headless screw 60 isthreaded thru the boss4 59.. A' cap 68a is threaded on the projectingend of the screw 6l and a gasket 60h is compressed between the cap andboss plug 59 to seal against pressure Ieak's from the compartment 58. .Acollar 6I is provided n the inner end of the screw 60 for abutting acoiled spring 62 thrusting against the valve 51 to urge the valveagainst the valve seat 56. Oil grooves 62a are provided around theperiphery of thel valve 51 for sealing the outer. end of the compartmentV58 from the chamber I4.

The compression of the spring 62 is adjusted by Y the screw 68 to holdthe valve 51 against 'the seat l 1 56 for retaining a predeterminedpressure in the chamber I3. When the pressure in the inlet chamber I3exceeds this predetermined amount, the valve 51.will be forced open toreturn the fluid into the return chamber I4 and back to the oil ta nk20.

Passages I3a, I4a, I5a and I6a respectively connect the chambers I3, I4,I5 and I6 with the conl trol chamber 4I at various points along the llength of the control chamber.

valve -seat 66 is threaded through the partition 65, as best shown inFigure 3.

A poppet valve 61 has a stem portion 68 vextending through the valveseat 66, a head portion 69 adapted to seat on the valve seat 66 for-separating the chamber I5 from thepassage I5a and a second stem portion10 extending outwardly from the head 69.

The chamber I5 isclosed by a plug 1I threaded intothehousi'ng portion40c. The plug 1I has a well 12 in the center portion thereof forslidably receiving therein the valve stem portion 10. A coiled spring 13 is held under compression between the plug 1I and the valve head 69for urging the valve head against the valve seat 66.

YThe valve stem 68 of the valve 61 receives a square or rectangularroller mounting 14 on the end thereof. The mounting .14 rotatablysupports a roller 15 adapted to ride on the surface The mounting 14 `andof the slidable core 53. roller 15 are disposed in a square orrectangular compartment 16 .broached out from a cylinderformed in thehousing 40c to prevent rotation of the mounting.

.An annular V-groove 11 is formed around the core 53 to dene camsurfaces 18 and 19 to act against the roller 15 for opening and closingthe valve v61 as the core 53 is moved in the control chamber 4I.

As best shown in Figures 3, 5 and 6, the slidable core member 53 has anaxial vertical wall 89 abutting thev top and bottom of thecasing 4I) andextending the full length Vof the core with the exception of the groovedportion 11 cut around the core. f'

The inner end of the core 53 has a solid disc portion 8l sliding againstthe entire circumferprevents an end thrust againstthe core thatv wouldotherwise effect an undesired sliding move- Yment out of the selectedposition for the core.

A solid masking portion 83 extends from-the vertical wall 88 of the corefor closing'that part of the mouth of the passage I3a on the same sideof the wall 88 as the masking portion, as shown in Figure 6. .Thismasking-portion 83 is quadrant shaped, as shown in Figure 6, to providea passageway 81 therebeneath.

The masking portion y83 is in spaced longithe same side of the wall 88as the masking portion 83 and to define a passageway therebeneathsimilar to the passageway l|11.

Oil entering the compartment 8 6 can freely rflow through thepassageways 81 under the masking portions 83 and 85 and around thegroove 11 of .the core into the passage I5a. The oil can v"likewisebleed through the groove 82 in the disc 8| to prevent an end thrust onthe core 53.

-A hollow masking portion 88' (Figures 3, 5 and 6) of semicylindricalshape extends from the oth- Y er side of the vertical wall 88 at a pointintermediate the masking portions 83 and 85. The' portion 88 has apassageway 89 therethrough.

This portion 88 is adapted to close the mouth of the passage 6a andthose portions of the passages |3a and Ma opening on this side of -thewall 88, as best shown in Figures 5 and G.

As shown in Figures 3 and 4, a fourth masking portion 98 of semicircularshape extends from the same side of the wall 88 as the portion 88 but isin spaced longitudinal relation from the portion 88.

A leg 9| extends from the portion 98 into spaced relation from theportion 88. The masking portions 88 and 98 therefore define acompartment 92 therebetween containing the leg 8|. 'I'he edge of the leg9| serves as a surface against which the roller 15 of the valve 61 can.with the groove 11 around the core for permitting iiow to and from thepassage |5a.

Operation of the valve mechanism The operation of the valves ofv thisinvention will be best understood from a reference to Figures 7 to 10inclusive, which show the various operating positions of the valve.A

' In Figure 7, the core 53 is moved to its innermost position in the'operating chamber 4I. In

this positionhalf of the inlet passage |3a communicates with thecompartment 86 between the masking portions 83 and 85. That portion ofthe passageway |3a on the other side ofv the wall 88 is closed by themasking portion 88.

The masking portion 85 closes that portion of the return passage Idaopening on the same side of the wall 8l as the open portion of thepassage Ila. The other half of the return passage Ila on the other sideof the wall 88 communicates n with the compartment 82.

` The mouth of the operating passage I6a comy municates with thecompartment 92 and'oil'can flow from this passage into the returnpassage Ila.

- The roller 15 on the valve 61 is contacting the peripheral surface ofthe core 53 to hold the valve open. 'I'he passage I5a therebycommunicates with the operating chamber I5.

With the core in the position shown in FigureV 7, therefore, oil fromthe inlet passage |3a ows into the compartment 86 and under the maskingportion 85 into' the operating chamber I5 from which it is fed to theupper ends ofthe hydraulic jack cylinder 25 and 26 throughthe pipe 22and tubes 23 and 24, as shown in Figure 1. This causes -the jackcylinders to raise, thereby lifting the work implement blade. Oil in the`jack -cylinders beneath the pistons 38 iows :through the tubes 28 -and29 and pipe 21 into the e operating chamber I6. The passageway I6a fromthe operating chamber is open so that the oil flows through thecompartment'92 in the control chamber II and from the compartment 92into the passageway Ida for return to the tank 28.

In the position of the valve shown in Figure 7,

therefore, the core directs fluid from the pump to the operating chamberI5 from which it is sent to the upper ends of the jack cylinders. Oilfrom the lower ends of the jack cylinders is returned to the tankthrough the operating chamber I6. Oil from the pump cannot flow back tothe tank because that portion of the passageway Ma on the same side ofthe wall 88 as the open passage I3a is closed by the masking portion 85.Likewise. oil from the pump cannot flow into the lower ends of thecylinders since that portion of the passage |31l on the other side ofthe wall ,88 is closed.

In the positionshown in Figure 8, oil is locked in the jack cylindersand can only flow between the cylindersvon the same sides of thepistons.

Thus the passages I3a and Ida are in communi-` cation through thecompartment 86 and through the hollow masking portion 88.

The'roller 15 on the valve 61 is disposed in the groove 11 ofthe core 53so that the passage I5a is separated from the operating compartment I5'by the closed valve 61. This prevents ow of oil from the tops of thejack cylinders into the valve.

` The operating chamber I6 communicating with the lower ends of the jackcylinders has its passageway I6a closed by the masking portion 88 of thecore 53, thereby sealing the oil in the lower ends of the jackcylinders.v 1

Oil from the pump I8 is merely recirculate back to the tank 28 throughthe passages I3a and |4a which are in full communication with eachother. The implement blade is thus held at a selected position andcannot move from this position, while at the same time the pump is notsubjected to a load.

'I'he next position of the valve is shown in Figure9, wherein the core53 is moved' a step outward from theposition shown in Figure 8. In thisposition the inlet passage I3a. on one side of the wall 88 of the coreis closed by the masking portion 83. However; the other half of theinlet passage |3a on the other side of the wall 88 is passageway I6.That portion of the return passageway I4a on the same side of the Wall88 as `the operating passageway IGa is closed by the masking portion 88.However,- the portion of the return passageway I4a on the other side ofthe wall 80 is in communication with the compartment 85.

The roller 'I5y on the valve 6T is in contact with theperipheral surfaceof the core 53 to hold the 10 valve open and join the operatingcompartment I5 with its passage I5a.

' In the position shown in Figure 9, therefore, oil from the pump 88passes through half of the passage I3a into the compartment 93 fromwhich l it is directed into the operating passageway I6a for flowinginto the operating chamber I6 and through thepipe 21 and tubes 28 and 29into the bottom ends of the jack cylinders 25 and 26. This will cause alowering of the jack cylinders to move the work implement bladedownward. Since oil is disposed above the pistons in the tops of thejack cylinders, this oil must be removed to permit the downward movementof the ycylinders. The oil can flow freely out of the tops of thecylinders through the tubes 23 and 24 into the pipe line 22. From thepipe line 22, the oil ows through the operating chamber I5, thepassageway I5a, the groove I1A of the core, the passageway beneath themasking chamber 85 and into the compartment 86. From the compartment 86the oil can freely flow back to the tank through the open half of thereturn passage a. In the position shown in Figure 9, therefore, oil isonly fed to the bottoms of the jack cylinders While the oil in the topsof the jack cylinders is allowed to return to the tank 20.

A movement ofthe core 53 to its outermost position in the operatingcompartment 4I as shown 40 in` Figure 10, permits the oil to ilovir`freely through the valve and to and from the cylinders and oil tank. Inthis position of the valve, the work implement blade is allowed to floatalong the ground level due to its own weight. 45.il As shown in Figure10 the inlet passage I3a on one side of the wall ,80 communicates withthe compartment 84. The inlet passage I3a on the other side of the wall80 communicates with l the compartment 93. Oil from the compartment 84can ow into the compartment 88 under the masking portion 83 as bestshown in Figure 6. The oil from the inlet passage I3a on both ysides ofthe wall-80 is therefore in communication with the return passage I 4aon both sides of the wall.

The operating passage IIa likewise communi-Av cates with the compartment93 and oil can freely ow through this pass/age. t

The leg portion 9| of the core abuts the roller 'I5 to open the valve 61and place the operating chamber I5 in communication with its passagewayI5a.

.With all of the passageways open, it is obvious that oil can flow intoand out of both ends of the jack cylinders through the valve while oilfrom the pump can return to the tank through the valve.

In all operating positions of the Valve, the space in the controlcompartment 4I between the disc` 8I and the end cap 42, receivesor-discharges oil through the bleeder passage 82 into the compartment84. This compartment 8 4 communicates beneath the masking member 83 asshown in Figure 6 with the compartment 88. In this,v 76 manner no endthrust is placed on thecore as the same is moved between its variousoperating positions.

In any position of the valve, if the pressure in the inlet chamber I3exceeds a predetermined maximum, the relief valve 51 will o'pen to retumthe olli to the tank 20.

From the above descriptions it should be understood that the valves ofthis invention are adapted to apply down pressure and up pressure tohydraulic jacks for raising and lowering work implement blades onbulldozers, snowplows and the like. These valves are also adapted tolock the implement Yblade in a desired position and to permit theimplement blade to float.

The valves operate by a simple sliding action of a core member which, inits sliding movement, controls the operation of a check valve.v Theslidable core can be greatly modified from the detailed constructiondescribed hereinabove. For example, a rearrangement of the ports in thevalve casing will permit the use of a core having grooves therein toconnect the ports and solid or ungrooved portions to mask the ports. Thecheck valve prevents return of liquid from the jack cylinders so as tolock the work implement blade in a desired position and when closedthereby prevents any increased liquid pressure in the jack cylindersfrom effecting an operation of the relief valve. This relief valve isoperative only to relieve increased oil pressure from the pump.

I am aware that many changes may be made and numerous details ofconstruction may be varied through a wide range without departing fromthe principles of this invention, and I, therefore, do not purposevlimiting the patent granted hereon otherwise than necessitated byv theprior art.

I claim as my invention:

1. A valve comprising a casing, partitions di-l viding the casing intoan inlet chamber, a return chamber, two operating chambers and a controlchamber, said casing having passages connecting each of the firstmentioned chambers with the control chamber, a valve seat between one ofsaid operating vchambers and its passage to the control chamber, anunbalanced valve normally vseated on the valve seat to separate saidpassage from the operating chamber, a core reciprocally mounted in saidcontrol chamber having cut away portions establishing communica'- tionthrough the control chamber between various of said passages, said corealso having solid portions for closing various of said passages, meanscarried by said unbalanced valve, riding on said core and said corehaving a cam surface adapted to contact said means for opening andclosing the unbalanced valve at selected positions of the core.

2. ,A valve mechanism comprising a hollow casing, a core slidable insaid casing, said core having an axial wall dividing the casing, aplurality of masking portions extending from both sides of said wall inspaced relation to each other, a V-shaped groove in one endof said core,an unbalanced poppet valve in said housing in spaced relation from thecontrol chamber, a roller carried by the valve adapted to ride in andout of the V-shaped groove of the core to open and close the valve, saidcasing having a plurality of ports adapted to be closed by said maskingportions and placed in communicationgwith each portions.

3. A valve mechanism comprising a casing defining an elongatedcylindrical control chamber,

an inlet chamber, a returnfcl/ianber and a pair of operatingchamberapssages connecting the inlet, return and operating chambers withthe control cl. amber alt/spaced areas along the length of thecontrol/chamber, an unbalanced poppet valve normally separating one ofsaid operating chambers vfrom its passage, a core slidably mounted inthe control chamber -to connect various of said passages with each otherthrough the control chamber, and'means carried by the pop,

pet valve riding on said core for opening the valve at selectedpositions of the core.

4. A valve mechanism comprising a-casingvdeilning an elongatedcylindrical control chamber, an'inlet chamber, a return chamber and ations to close the other portions of the passages l whereby a sliding ofthe wall will control flow of fluid between the passages.

- 5. In a valve mechanism comprising a casing deiining a cylindricalcontrol chamber, an! operata sage whereby ilow of'fluid through thepassages ing chamber, an inlet chamber and a return chamber, a dividingwall slidable longitudinally in said controlchambcr, passages joiningthe inlet and returnchambers'with the control chamber on both sides oithe wall at spaced areas along the control chamber, a passage joiningsaid op- 'erating chamber with said control chamber on one side only ofsaid wall between the rst mentioned passages, a hollow semicylindricalmasking portion extending from one -side or said wall to selectivelyclose the passages and to permit fluid ow therethrough' between theVinlet and return' passages while closing the operatingy chamber passage,and spaced solid quarter circular masking portions extending from theother side of said wall to selectively close the inlet and returnpassages on said side 'of the wall alternately with a closing of theoperating pas-- is controlled by a sliding of thejwall.

6. A valvemechanismrcomprising a housing defining l`a central elongatedcontrol chamber,

deilning an inlet chamber anda separate re- Y turn chamber, passagesconnecting the inlet-and return chambers with the. control chamber, aseparate passage in said integral housing por--I tion4 joining the inletand return chambers, a relief valve normally closing said passage, saidconnecting the operating lchamber with the control'chamber, anunbalanced valve separating the operating chamber from its passage,.acore slidable in the control chamber to direct iluid ilow 4between thepassagesv and said core avingcam surfaces to loperate said unbalancedvalve.

said housing having an integral portion thereof housing havinga secondintegral housing portion defining an operating chamber, a passage '1.Avalve mechanism .comprising a casing `de` fining a control chamber, aninlet chamber, a

y return` chamberanda'pairoi operating chambers,said casing having portsjoining the inlet,

return and operating chambers with the control chamber at spaced areastherealong,an unbal .anced valve in the outlet side of one of saidoperating chambers'to1 seal the chamber from its port, a corereciprocally mounted in said control chamber and having a cam surface tooperate the unbalanced valve, masking portions at spaced intervalsalongsaid core to selectively close said ports, said masking portionsdening compartments therebetween in the control charnber to operativelyjoin said p orts and determine the effective length of the controlchamber, and means outside of said casing to reciprocate the core forselectively directing iuid to and from one or both of the operatingchambers.

8. In a uid pressure jack assembly having a jack cylinder, a piston inthe cylinder in -slidable relation thereto, a pair of conduits eachcommunicating with an opposite end of the cylinder,

a source of uid for operating the piston, a,

pump for propelling said fluidunder pressure through the conduits to thecylinder, and a tube for returning iluid from the cylinder to lsaidsource, the improvement which comprises a valve mechanism for directingliquid ilow to and from the cylinder, said mechanism including a casingdening a pair of `operating chambers each in communication with one ofsaid conduits and an elongated control chamber `in communication atspaced areas along the length thereof with said operating chambers, anunbalanced valve in one of said operating chambers separating saidAchamber from the Ycontrol chamber, and a core movable in said controlchamber to direct uid ow to and fromthe ends of the jack cylinders andto actuate said unbalanced valve for permitting such flow.

9. A valve mechanism comprising a an inlet chamber, a return chamber,and an operating chamber,l passages connecting said inlet,

return and operating chambers with said control chamber at spaced areasalong the length of the control chamber, an, unbalanced poppet valvenormally separating said operating chamber' from,its passage, a core,slidably mounted4 in the control chamber to connectvarious of saidpassages with each other through the control chamber, and means carriedbythe poppet valve riding on said core for opening the valve at selectedpositions of the core.

0. Valve mechanism comprising a casing deng a main control chamber, aninlet chamber, a return chamber, land anoperating chamber,

trol Ychamber at spaced apart points therein, an

casing dening an elongated cylindrical control chamber,

- said casing having passageways joining the inlet," return, jandoperating chambers with the conunbalanced valve normally separatingthe'op- .v

slidably mounted in the control chamber to con'- erating :chamber fromits passageway, a core nect various of said passageways witheach other ithrough the control chamber, and means on said core .controlling saidunbalanced'valve to selectively allow and check rluid flow between ,thecontrol chamber and .operating chamber.- 11. A valvecomprising a casingdening an Aelongated control chamber,vsaid control chamber having aplurality of ports communicating therewith at spaced points along thelength thereof, a core slidable in said chamber a di-v l viding wallextending.- axially thereof', said wall having the longitudinal edgesthereof in slidable vengagement with the chamber wall, av solid end diskon said core engaging the chamber Wall yaround the periphery thereof,masking portions' extending at spaced intervals fromsaid dividing. wallinto slidable engagement with said chamber wall adapted to selectivelyclose or open said ports to the control chamber when the core is movedto respectively position them over o r displaced from said ports, saiddividing wail, end disk, and

lsaid compartments with a closed end of the chamber beyond the core tobleed uid through the disk for equalizing pressures on both sidesthereof to balance fluid end thrusts on the core.

12. A valve comprising a casing defining an elongated control chamber,said chamber'having aninlet port, an outlet portfand an operating portcommunicating with said chamber at spaced apart areas' thereof, a coreslldable in said casing having spaced apart masking portions in'slidable engagement with the chamber walls adapted to close said portswhen the core is moved to position them over the ports, .said coredening compartments between the masking portions for placing various ofthe ports in communication, a solid end portion on said core slidableengaging the chamber wall around its periphery, one face of the solidend portion defining an end wall for the compartments adapted tocommunicate with the inlet and outlet ports,

the opposite face of said end portion facing a closed end of thechamber, and said solid end having a bleeder passageway therethroughjoining the opposite faces thereof whereby iiuid is free to ow betweenthe compartments and said closed end of the chamber to relieve endthrusts on the core and maintain the set positions there- 13. A valvemechanism comprising a casing dening a control chamber having aplurality of ports along the length thereof communicating with saidchamber, a core slidable in said casing having recessed portions alongthe length thereof adapted to place various of said ports-incommunication, said core also having masking portions inslidableengagement with the chamber wall to close said ports whenpositioned opposite said` ports, a solidend wall on said core engagingthe chamber wall around. substantially the entire periphery thereof,said end wall having one face thereof defining an end of at least o'nerecessed portion of the core and having an opposite face thereofdellning the inner end of a blind compartment in the control chamber,and.

HARRY c. BUFEINGTON.

